Underwater completion



- Jan.14, 1969 NF. MANNING 3,421,579

UNDERWATER COMPLET ION Filed June 17, 1965 FIG I INVENTOR WlLLlAM EMANNING BY CZZQN 12 (6M United States Patent 4 Claims ABSTRACT OF THEDISCLOSURE This specification discloses apparatus for providing alife-sustaining environment in an area adjacent to and surrounding asubmerged production wellhead. The apparatus comprises a base structureincluding an upper and lower base connected by an open framework, and achamber mounted on the base capable of retaining air. The base structureis either mounted directly on the marine bottom, if the respectivewellhead is located just above the marine bottom, or the base structuremay be fixed to a caisson structure above the marine bottom, if thewellhead is afiixed atop such a caisson structure for spacing thewellhead above the marine bottom at a convenient diving depth. Thechamber is mounted on top of the base and has a scalable entry portabove the lower end thereof. The chamber may also be open at the lowerend so that a diver-workman can enter through the framework of the basestructure which spaces the chamber at least far enough above the marinebottom for such a diver-workman to enter. Means is provided forproviding a breathable atmosphere inside the chamber when maintenanceoperations are necessary. This last stated means can be an air hoseconnected to a port extending through the wall of the chamber or, if thelower end of the chamber is open, an air hose may be extendedtherethrough, the other end of the hose being connected to an air pumpon a surface vessel floating above. In some instances the chamber may bereleasable from the base structure so that it can be lifted to thesurface to serve a second function, that of a traveling chamber totransport a workman to the wellhead. When the wellhead is not beingserviced, the chamber can be filled with a protective fluid to preventan attack on the wellhead by sea water and/ or undersea life.

The invention relates to a facility for servicing a submerged productionwellhead, more particularly to a facility capable of permitting aworkman to service the submerged wellhead without being restricted bypersonal life-sustainin g equipment.

In coastal offshore waters where fluid mineral deposits, i.e., oilexists in the subaqueous formations underlying the marine bottom, it isusually inconvenient, and many times impractical, to complete a wellabove the surface of the body of water. In such instances the well canbe completed near the marine bottom and the minerals produced throughflow lines connected to the submerged wellhead. Although a submergedproduction wellhead design may successfully overcome some of the designproblems previously encountered when the wellhead is extended above thesurface, for example, the forces on the wellhead and the dependingcasing, caused by the action of waves on the wellhead, new problems arecreated in conjunction with the servicing thereof. Being situated nearthe bottom of a body of sea water, the wellhead is in a hostileenvironment. It is under continuous attack from marine life and thecorrosive effects of the salt water itself. The equipment must bechecked periodically, crustaceous deposits removed, and corrodedequipment replaced.

Although robot equipment has been suggested for serv- 3,421,579 PatentedJan. 14, 1969 icing submerged wellheads, it has been found that aworkman can do a more efiicient job in a shorter time, particularly ifhe is not encumbered by personal lifesustaining equipment, such as adiving suit, or limited by the time in which he can work at the requireddepth. Therefore, one of the new problems created by having the wellheadnear the bottom is how to provide an environment in which a man can workon the submerged wellhead without personal Ilife-sustaining equipment.Another is how to protect the production wellhead from the hostileenvironment.

Accordingly, it is an object of this invention to create an environment,at a submerged wellhead, in which a man can work on the wellhead withoutthe encumbering restrictions of personal life-sustaining equipment.

It is another object of the invention to provide a well servicingfacility with a base structure surrounding the submerged well casing, onwhich a diver may work when servicing the wellhead, and which may serveas support for an air chamber enclosing the production wellhead itself.

It is a further object of the invention to provide a wellhead servicingfacility which is designed to allow a diver-workman lowered to theproduction wellhead to work thereon without personal life-sustainingequipment.

It is another object of the invention to provide a method for servicinga submerged production wellhead with a diver-workman including havingthe diver-workman enter the air chamber from the surrounding water, sealthe chamber, and provide a life-sustaining atmosphere in the chamberwhereupon the diver-workman can remove his personal life-sustainingequipment before servicing the production wellhead equipment.

It is still a further object of the invention to provide a protectiveenvironment for the production wellhead to reduce maintenance time.

All the objects and advantages of the invention will become apparentfrom the following description and from the accompanying drawings inwhich:

FIGURE 1 is a side elevational view of the production wellhead servicingfacility of the present invention which includes a base structure and anair chamber, the base structure being shown through section line 11 asindicated in FIGURE 2;

FIGURE 2 is a top plan view of the base structure, taken through line 22of FIGURE 1, illustrating the framework of the base structure designedto support the air chamber.

In accordance with the present invention, a hollow airretaining chamberencases a production wellhead of a completed well and is supported on abase structure. The base structure consists of an open framework and isanchored by a number of shear plates or spuds rigidly fixed thereto, anddriven into the marine bottom. Also, casting slips are operativelyconnected between the base structure and the well casing, below thewellhead, to help anchor the structure when the chamber is evacuated ofwater and filled with air. In this connection, the term air is used inthe generic sense to connote any breathable mixture of gases. Awalk-around platform circumscribes the base structure at the upper endof the framework beneath the base of the air chamber.

The air chamber is a vertical cylinder surrounding the well head andclosed at least at its upper end. The air chamber, being spaced from themarine bottom on the open framework of the base structure, is situatedso that a diver-workman can enter through an opening in the bottomthereof. A sealable emergency manhole or entry port is formed in the airchamber to permit a man to escape from the enclosed space if the lowerend of the air chamber becomes blocked. If the manhole emergency entryport is used to gain entrance to the air chamber,

air must be reintroduced and the water expelled, before the workman canremove his personal life-sustaining equipment in preparation forstarting theservicing operation. While in the usual case the air chamberbolts or otherwise rigidly connects to the base structure, the airchamber may be releasably connected to the base structure so that thechamber can be raised to the surface at will. A workman can then descendwith the chamber, obviating the need for personal life-sustainingequipment at any stage. In another embodiment, the air chamber is boltedpermanently to the supporting structure and when not in use, as a meansto permit a diver-workman to service the wellhead Without personallife-sustaining equipment, is filled with a light oil or some othersubstance which deters marine life from attacking the productionwellhead and prevents the corrosive action of the salt water upon themetal parts thereof.

Referring now to the drawings, a submerged well servicing facility,generally designated 10, consisting of a base structure 12 and asubstantially cylindrical air chamber 14, is shown surrounding a wellcasing 18, extending up from beneath the marine bottom and a submergedproduction wellhead 16 capping the well casing 18. The base structure 12consists of a framework of beams forming parallel octagonal bases, alower base 22 and an upper base 24, spaced apart by a number of fixedstruts 26 converging upwardly from the larger, lower base 22 to thesmaller, upper base 24. A flow line 27 for the produced minerals, andany other necessary lines connected to the wellhead 16, exits from theenclosed air chamber 14 through an opening in the bottom thereof andthrough the open framework of the base structure to productionfacilities (not shown). A casing slip assembly 28, which is adapted togrip the well casing 18 adjacent the bottom 20 is centrally mountedwithin the base structure 12 by means of diverging struts 30 extendingupwardly from the perimeter of the casing slip 28 to the perimeter ofthe upper base 24. The base structure 12 is also anchored on the marinebottom 20 by means of a number of integral spuds 32 depending verticallyfrom the lower base 22 and driven into the formations underlying themarine bottom 20. Between the spuds 32 and the casing slip assembly 28,the platform 12 and air chamber 14 are securely positioned adjacent themarine bottom 20, below the surface of the body of water. To overcomethe buoyancy of the air chamber 14, additional weight, such as scrapiron, may be attached to the framework of the base structure 12.

The cylindrical air chamber 14 is fixed atop the upper base 24 adjacentan encircling walk-around platform 34, welded to the base structure 12and extending radially outward several feet therefrom to provide a solidfooting for a diver-workman servicing the wellhead 16. A flooring (notshown) may be included between the bottom of the air chamber 14 and theupper base 24 for a diverworkman to stand on within the air chamber 14.A cover 36, serving to seal releasably entry port 38, formed in theupper end of chamber 14, enables a diver-workman to enter the airchamber 14 while the chamber 14 is submerged and filled with water, orother fluids, as later discussed. The lower end of a buoy line 39 isfixed to the upper end of the air chamber 14 and is connected, at itsupper end (not shown) to a buoy for locating the air chamber 14 from thesurface.

An air hose (not shown), terminating with a quick release coupling, aswell known in the art, is adapted to be operatively connected to theinterior of the chamber 14 by a port 40, extending through the outerwall thereof. The port 40 is located in a position where it may bereached by a diver (not shown) standing on the walkaround 34, enablingthe diver-Workman to couple the air hose to the port 40 to introduce airinto or circulate air through the chamber 14 under the control of pumpson the surface (not shown). If the chamber 14 is bottomless, or at anyrate is not completely closed, the air hose may alternatively extend upinto the chamber 14 from beneath (not shown). It would be necessary tohave an unbroken flooring only if the wellhead 16 were deeply submergedin the water and it would be desirable to have the air in the chamber atless pressure than the water at the working depth.

The base structure 12 is anchored in place prior to the completion ofthe Well (not shown) and may even be anchored in place prior to drillingthe well, being used as a guide means for stabbing in the well casing18. In any event base structure 12 must be in place before productionwellhead 16 is connected to the well casing 18, while the air chamber 14bolts in place after the well is completed and the well casing 18 iscapped by the production wellhead 16. The walk-around 34 may be used bya diverworkman for connecting up the wellhead 16 prior to theintroduction of the air chamber 14, since the submerged land adjacentthe wellhead 16 is often too soft to provide suitable footing, or thetop of the well casing 18 may be too far above the marine bottom 20 topermit installation of the production wellhead 16 by a diver-workmanstanding thereon. The air chamber 14 secures rigidly to the upper base24, as discussed above, or connects thereto by a number of releasablelocks 42. If the air chamber 14 releasably connects to the basestructure 12, it may be brought to the surface for a workman to enterthereinto without the aid of any diving apparatus; the entry port 38 andcover 36 can then be relegated to function only as an emergency escapehatch. In this instance the chamber 14 is brought to a position abovethe surface and is then ballasted with enough weight so distributed thatit will remain in the vertical position as it is lowered through thewater filled with air. As the chamber 14 approaches the well thediver-workman inside can guide it over the production wellhead 16, or anumber of the various types of guide ropes, or stab-in connections, asshown in the prior art, can be used for guiding the air chamber 14 intoconnection with the base structure 12. If a floor is constructed on theupper base 24, and sealed to the well casing 18, a circumferential seal(not shown) may also be included around the base of the chamber 14 toprovide a watertight connection therebetween, or it may be open beneaththe air chamber 14, with air pressure therewithin keeping the water out.Of course, with the air chamber 14 also providing underwatertransportation, the releasable locks 42 would be therewithin to obviateneed for any operations to be performed in the open water.

An air chamber 14 of the permanently fixed type, may be used, when notoccupied by a diver-workman, as an environmental shield containing oilor a noncorrosive gas for preventing an attack on the productionwellhead 16 by the corrosive action of the sea water and/ or bybarnacles, or other types of undersea life which will quickly cover anexposed device and cause heavy formations on and extensive damage to thewellhead 16.

A wellhead servicing facility 10, such as discussed herein, is designedfor use in oifshore or costal areas where the water is approximatelyfeet or so deep. There is no reason, however, why it cannot also be usedwhen the water is much deeper, even 1500 feet. Such a servicing facility10 may also be used where the water is extremely deep but the well iscompleted at a point considerably above the ocean floor. In such aninstance a large submerged caisson or support structure would extendfrom the ocean floor to the lower base 22, or the base structure 12could be held in position solely by casing slips connected to the wellcasing 18.

Although the present invention has been described in connection withdetails of the specific embodiments thereof, it is to be understood thatsuch details are not intended to limit the scope of the invention. Theterms and expressions employed are used in a descriptive and not alimiting sense and there is no intention of excluding suoh equivalents,in the invention described, as fall within the scope of the claims. Nowhaving described the apparatus and methods herein disclosed, referenceshould be had to the claims which follow.

What is claimed is:

1. A servicing facility for a submerged wellhead located above a marinebottom and below the surface of a body of water, said wellhead beingoperatively connected to a well casing extending beneath said bottom ofsaid body of water, comprising an air-retaining chamber, the weight ofsaid chamber being supported beneath said surface on a base structure ina position in which said chamber encases said wellhead, said basestructure having at least one casing slip assembly means encircling andgripping said well casing below said wellhead whereby said chamber isheld in position by said base structure when said chamber is buoyant aswell as when said chamber is not buoyant, means for selectivelyintroducing air into said chamber to fill substantially said chambersurrounding said wellhead, and means for permitting a workman to entersaid chamber whereby a workman can service said wellhead without beingencumbered by personal life-sustaining equipment.

2. Said wellhead servicing facility of claim 1, wherein said basestructure extends from marine bottom to said chamber, and means foranchoring said base structure into said marine bottom.

3. A wellhead servicing facility for a submerged wellhead located abovea marine bottom and below the surface of a body of water, said wellheadbeing operatively connected to a well casing extending into a wellbeneath said marine bottom of said body of water, comprising; anair-retaining chamber encasing said wellhead and a base structuresurrounding said well casing below said chamber for supporting saidchamber; said chamber having a cylindrical shape oriented so that itsaxis of formation is vertical, a closed upper end of said chamber, anentry port in Said closed upper end, a cover for said entry port formingan airtight seal therewith when said entry port is closed by said cover,means for selectively introducing air into said chamber to displace anyother fluid therewithin; said base structure being constructed of anupper base and a lower base surrounding said well casing, strutsinterconnecting said bases to provide an open framework, a casing slipassembly rigidly supported within said base structure and gripping saidwell casing to prevent upward movement of said base structure, integralspud means depending from said lower base into said marine bottom toanchor said base structure, a circular walk-around platform surroundingsaid base structure adjacent said upper base, and means for connectingsaid base structure to said chamber at the lower end thereof.

4. A servicing facility for a submerged wellhead located above a marinebottom and below the surface of a body of water, said wellhead beingoperatively connected to a well casing extending beneath said body ofWater, comprising an air-retaining chamber, said chamber being supportedbeneath said surface on a base structure in a position in which saidchamber encases said wellhead, a circular walk-around platform supportedon said base structure adjacent the upper end thereof, said walkaroundplatform extending outward of said chamber when said chamber issupported on said base structure whereby said walk-around platform canbe used by a diver-workman, wearing personal life-sustaining equipment,to connect said chamber to said base structure or to connect saidwellhead to said casing prior to the installation of said chamber, meansfor selectively introducing air into said chamber to fill substantiallysaid chamber surrounding said wellhead, and means for permitting aworkman to enter said chamber whereby a workman can service saidwellhead without being encumbered by personal life-sustaining equipment.

References Cited UNITED STATES PATENTS 3,353,364 11/1967 Blanding et a1166-.5 1,948,934 2/ 1934 ORourke 61-69 2,190,330 2/1940 Martine 61-692,534,480 12/1950 Shannon -8 2,667,751 2/ 1954 Osborn 61-69 2,747,8405/1956 Miles 166-.5 X 2,783,970 3/1957 Gillespie 166-.5 X 2,854,2159/1958 Cox et al. 166-.5 2,906,500 9/1959 Knapp et al 166-.5 3,004,60210/1961 Kofahl 175-8 3,294,185 12/ 1966 ONeill et al. 166-.5 X

FOREIGN PATENTS 160,865 4/ 1921 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner.

US. Cl. X.R.

